Oxygen uptake of the human fetus at term

Objective. To measure oxygen uptake of term human fetuses and compare the values between those delivered vaginally following normal labor and those delivered by cesarean section before the onset of labor. Design. This was a prospective cross-sectional study. Setting. University teaching hospital. Sample. Twenty healthy pregnant women at term (38-42 weeks) were included in this study. Among them, 10 were delivered by elective cesarean section and 10 had normal vaginal delivery. Methods. Umbilical vein volume blood flow was measured 24 hours before delivery. Immediately after delivery, the fetal weight was determined, and the umbilical venous and arterial blood samples were obtained. Blood gas analysis was performed and hemoglobin content was measured. Fetal oxygen uptake was calculated as a product of umbilical venous blood flow and the difference in the umbilical arterial and venous oxygen content. Results. We found that the mean oxygen uptake in human fetuses at term (median gestational age 39 weeks) to be 6.58 ml/min/kg (i.e. 0.29 mmol/min/kg). There was no significant difference in oxygen uptake between fetuses delivered following uncomplicated normal labor and those delivered by elective cesarean section before the onset of labor. Conclusion. Oxygen uptake of the appropriately grown normal human fetus at term is approximately 6.6 ml/kg/min and is not significantly affected by normal labor and delivery. Human fetuses tolerate intermittent reductions in uterine blood flow and oxygen supply associated with myometrial contractions during normal labor quite well.